Group III nitride wafer and its production method

• US 8,921,231 B2
• Filed: 03/15/2013
• Issued: 12/30/2014
• Est. Priority Date: 04/07/2006
• Status: Active Grant

• Current Assignee: Seoul Semiconductor Co., Ltd.
• Original Assignee: Seoul Semiconductor Co., Ltd., SixPoint Materials, Inc.
• Inventors: Hashimoto, Tadao, Letts, Edward, Hoff, Sierra
• Primary Examiner(s): SMITH, BRADLEY
• Application Number:
  US13/835,636
• Publication Number:
  US 20140065796A1
• Time in Patent Office: 655 Days
• Field of Search: 438/690, 438/691, 438/693
• US Class Current: 438/693
• CPC Class Codes: C30B 29/403 AIII-nitrides
• CPC Class Codes: C30B 29/406 Gallium nitride
• CPC Class Codes: C30B 33/00 After-treatment of single crystals or homogeneous polycrystalline material with defined structure C30B31/00 takes precedence
• CPC Class Codes: C30B 33/10 in solutions or melts
• CPC Class Codes: C30B 7/105 using ammonia as solvent, i.e. ammonothermal processes
• CPC Class Codes: H01L 21/02013 Grinding, lapping
• CPC Class Codes: H01L 21/02019 Chemical etching
• CPC Class Codes: H01L 29/2003 Nitride compounds
• CPC Class Codes: H01L 29/201 including two or more compounds , e.g. alloys H01L29/2006 takes precedence

Abstract

The present invention discloses a group III nitride wafer such as GaN, AlN, InN and their alloys having one surface visually distinguishable from the other surface. After slicing of the wafer from a bulk crystal of group III nitride with a mechanical method such as multiple wire saw, the wafer is chemically etched so that one surface of the wafer is visually distinguishable from the other surface. The present invention also discloses a method of producing such wafers.

Claims

1. A method of fabricating a group III nitride wafer having a first layer and a second layer, each comprising a damaged or partially damaged layer of group III nitride, and a third layer having highly oriented poly or single crystalline group III nitride, comprising:

(a) slicing a wafer from a bulk crystal of a group III nitride ingot mechanically to form the first layer and the second layer;

(b)before chemically-mechanically polishing the wafer, chemically etching the wafer under conditions that make the surface of the second layer visually distinguishable from the surface of the first layer.

2. A method according to claim 1, wherein the wafer is cut from the ingot using a multiple wire saw.

3. A method according to claim 1, wherein the chemical etching uses phosphoric acid or its mixture.

4. A method according to claim 1, wherein the chemical etching uses phosphoric acid or its mixture at 50°

C. or higher.

5. A method according to claim 1, wherein the density of line defect and grain boundary of the third layer is less than 10⁶ cm⁻

2.

6. A method according to claim 1, wherein the group III nitride comprises GaN.

7. A method of fabricating a group III nitride wafer comprising removing the first layer or the second layer of a wafer of claim 1 and exposing the third layer with a surface quality sufficient to fabricate devices.

8. A method according to claim 7, wherein the removing process comprises grinding.

9. A method according to claim 7, wherein the removing process comprises lapping.

10. A method according to claim 7, wherein the removing process comprises polishing.

11. A method according to claim 7, wherein the removing process comprises chemical mechanical polishing.

12. A method according to claim 7, wherein the group III nitride comprises GaN.

13. A method according to claim 1, wherein said bulk crystal was formed using supercritical ammonia.

14. A method according to claim 12, wherein said bulk crystal was formed using supercritical ammonia.

15. A method according to claim 1, wherein a plane at the surface of the first layer is nonpolar and wherein the surface is miscut to the nonpolar plane a sufficient amount that the surface is polar.

16. A method according to claim 1, wherein the step of etching the wafer is performed before a step of lapping the wafer.

17. A method according to claim 1, wherein the method further comprises using a visual distinction between the surface of the first layer and the surface of the second layer to determine which of said layers to process in a subsequent processing step.

18. A method according to claim 17, wherein the subsequent processing step is selected from the group consisting of (a) lapping and (b) polishing.

19. A method according to claim 18, wherein the method further comprises forming a device on the wafer.

20. A method of fabricating a GaN wafer having a first layer and a second layer, each comprising a damaged or partially damaged layer of GaN, and a third layer having highly oriented poly or single crystalline GaN, comprising:

(a) charging Ga-containing nutrient in a reactor;

(b) charging at least one seed crystal in the reactor;

(c) charging a chemical additive which increases dissolution of Ga-containing nutrient into supercritical ammonia;

(d) charging ammonia in the reactor;

(e) sealing the reactor;

(f) providing enough heat to ammonia to create supercritical state;

(g) dissolving the Ga-containing nutrient into the supercritical ammonia;

(h) crystallizing GaN on the seed crystal to form a bulk crystal of a GaN ingot;

(i) slicing a wafer from the bulk crystal of the GaN ingot mechanically; and

(j) chemically etching the wafer under conditions that make the surface of the second layer visually distinguishable from the surface of the first layer.